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Biomedical subjects

C Prati

Publications and source records attributed to C Prati.

At least 37 records · Page 2Linked to original sources
PubMed2001

Treatment of cervical dentin hypersensitivity with resin adhesives: 4-week evaluation.

PURPOSE: To evaluate the effectiveness of a dentin bonding agent containing HEMA compared to a resin emulsion in the reduction of cervical dentin hypersensitivity (CDH). MATERIALS AND METHODS: The study was a randomized-within-subject, double blind design. Twenty patients who were suffering from CDH from at least two teeth (canines and/or premolars) were enrolled. The subjective perceptions of pain in response to tactile, air blasts and cold ethyl chloride stimuli were evaluated using a visual analog scale (VAS) at baseline and 10 minutes, 1 week and 4 weeks after the treatments. Scotchbond 1 (a dentin bonding agent similar to Single Bond in the USA) and MS Coat (a resin emulsion), both applied according to the manufacturers' directions, were selected for the study. RESULTS: Multiple regression ANOVA for repeated measures showed that both treatments significantly reduced the CDS with respect the baseline values after just 10 minutes. There were no significant differences between the ability of the two treatments to reduce CDH for each of the three evaluation stimuli or for subjective evaluation.

Adult↗
PubMed1999

Effect of removal of surface collagen fibrils on resin-dentin bonding.

OBJECTIVES: The aim of this study was to evaluate the effects of NaOCl at removing the demineralized layer by examining the morphology of the hybrid layer and measuring shear bond strengths after different dentin treatments. METHODS: Dentin disks were treated with: (1) 35% phosphoric acid (PA) 20 s; (2) PA treatment followed by 1.5% NaOCl, 2 min; (3) PA treatment, followed by a 10% NaOCl immersion for 120 h. SEM was used to analyze the morphology of dentin and its interface with dentin bonding agents (DBAs), while shear bond strength tests were used to measure adhesion. All specimens were then fractured into two halves: One half was inspected under SEM; the other half was sequentially placed in 10% PA followed by 12.5% NaOCl for 70 h, to remove all dentin from the resin replica of the original bonded interface. RESULTS: SEM observations showed that collagen fibrils were completely removed from the acid-etched surface by NaOCl treatment. The diameter and the size of dentinal tubules and the number of lateral branches of the tubules were increased following NaOCl treatment. NaOCl applied on dentin smear layers did not significantly modify their SEM morphology. Resin tags were larger in diameter after phosphoric acid/NaOCl treatment than after only phosphoric acid treatment. Resin-infiltrated dentin-layers were only observed after the single phosphoric acid (i.e. conventional etching) procedure, and were not observed after combined phosphoric acid/NaOCl treatment. Etched/NaOCl samples showed a lower bond strength using Scotchbond MP and 3M Single Bond, but were higher in Optibond FL and unmodified in Prime & Bond 2.0 groups when compared with acid-etched controls. Treatment of etched dentin with NaOCl for 120 h produced an unusual type of resin infiltration of mineralized dentin that could be called a "reverse hybrid layer" which may explain the mechanism of resin bonding to NaOCl treated dentin. SIGNIFICANCE: The use of acidic conditioners for exposure of the collagen matrix exposes a soft delicate mesh that can collapse, thereby interfering with resin infiltration. If acid-etching is followed by NaOCl treatment, high bond strengths can be achieved via "reverse hybrid layer" formation, a proposed new mechanism of micromechanical resin retention. This mechanism is not yet recommended for clinical use but demonstrates a new type of resin retention.

Adolescent↗
PubMed1999

Effect of air, dentin and resin-based composite thickness on light intensity reduction.

PURPOSE: To evaluate the effect of air, dentin and resin-based composite thickness on light intensity reduction. MATERIALS AND METHODS: Two different light-units were used in the study. Light intensity was measured using a curing radiometer. RESULTS: There was an exponential decrease in light intensity with distance. The light-intensity value at a specific distance from the tip during passage through a specific dental material was calculated. Both composite and dentin caused a dramatic reduction in light intensity rate, e.g. 2.0 mm of composite are sufficient to reduce the light-intensity to 6% of its initial value.

Air↗
PubMed1999

Dentin permeability after toothbrushing with different toothpastes.

PURPOSE: To evaluate the interaction of smear layer produced during brushing and dentifrice particles. MATERIALS AND METHODS: Dentin disks were obtained from extracted human third molars. Dentin permeability was evaluated using a hydraulic pressure apparatus working at 1 psi of pressure. After preparation, each sample was connected to the hydraulic pressure apparatus to evaluate the permeability of dentin with the smear layer produced during specimen preparation. After 5 min of measurements dentin was etched with 37% phosphoric acid gel for 2 min, washed and gently dried with cotton to measure the permeability after smear layer removal. This was done to measure the maximum permeability of each specimen (expressed as 100%). Then a second smear layer was produced using a #400 carbide paper under water for 1 min. Dentin permeability of the smear layer covered dentin was then measured, and expressed as a percent of the maximum permeability of that specimen, permitting each specimen to serve as its own control. The three toothpastes used (Merfluan powder, Merfluan paste and Fluorigard) were applied on dentin surfaces using a small sponge to completely cover the dentin surface. After 5 s, each sample was connected to a mechanical device and brushed under water for 3 min with constant pressure of 250 gr using a Colgate medium toothbrush. After this treatment, each sample was gently washed with tap water, gently air dried for 3-5 s and connected with the pressure apparatus to remeasure the permeability after brushing. For SEM examination of dentin before and after treatment with toothpaste and brushing, each dentin and enamel sample was fixed in 2% buffered glutaraldehyde. RESULTS: Dentin permeability proved unaffected by dentifrice treatments. SEM observations demonstrated the presence of dentifrice particles on dentin surface and inside dentin tubules. Smear plugs produced during dentin brushing were not removed by dentifrices.

Dentin↗
PubMed1999

Calcium phosphates produced by physical methods in the treatment of dentin hypersensitivity.

BACKGROUND: The aim of this paper is to study the properties of innovative materials based on defective calcium phosphates produced by physical methods in the therapy of dentin hypersensitivity. METHODS: In particular, the effects of gels, aqueous solutions and toothpastes containing the above mentioned materials on dentinal permeability measured as dentin hydraulic conductance have been studied. The calcium phosphates have been characterized by X-ray powder diffraction (Rietveld analysis) and Fourier transform infra-red analysis. In addition, scanning electron microscopy has been performed to study the surface of dentin and enamel after treatment with the phosphates. In particular sound occlusal dentin, sound cervical dentin, carious occlusal dentin, sound buccal enamel and carious buccal enamel have been observed. RESULTS: The results have shown that these biocompatible materials can be produced with chemical and physical characteristics very similar to dentin and/or enamel. By forming a protective layer inside and outside the dentin tubuli, the calcium phosphates significantly reduce the dentinal hypersensitivity. CONCLUSIONS: These phosphates seem to be a promising material for clinical application.

Calcium Phosphates↗
PubMed1999

Bioactivity of chitosan in dentistry. Preliminary data on chitosan-based cements.

BACKGROUND: The chemical association of chitosan with inorganic salts, such as calcium phosphate, finds a promising application in dentistry as room-temperature self-hardening cement. We present the physical, chemical and crystallographic characterization of newly-developed cements made of 1) calcium-phosphate and a chitosan gel obtained by acetic acid treatment, and 2) calcium phosphate and a chitosan gel obtained by ascorbic acid treatment. Both cements are self-hardening at room temperature. METHODS: The cements were characterized by X-ray diffractography, scanning electron microscopy and fluorine-selective electrode analysis. RESULTS: The chitosan-hydroxyapatite cements had hardness comparable to spongy bone and above that of PMMA. CONCLUSIONS: The cements are promising for application in endodontics and restorative dentistry.

Biocompatible Materials↗
PubMed1998

Retention and marginal adaptation of a compomer placed in non-stress-bearing areas used with the total-etch technique: a 3-year retrospective study.

The aim of this clinical study was to evaluate class V and class III cavities restored with a polyacid-modified resin composite (compomer) restorative material in association with two different dentin-enamel bonding systems: Dyract-PSA (Primer Sealer Adhesive-DentSply, Germany) and Prime & Bond 2.0 (DentSply, Germany). The control group was a hybrid composite used with ProBond bonding system (DentSply, Germany). A total of 116 restorations (79 class V, 37 class III) were made and reevaluated after 1, 2 and 3 years in 55 patients in two private practices and in a university department. Class V nonretentive cavities were located at the CEJ level and class III at interproximal level close to CEJ. Each cavity was prepared using a water-cooled, high-speed handpiece with a fine diamond burr. A small bevel was prepared along enamel margin. Cavity dimensions were no more than 3.5 x 3.5 mm (using burr as reference point). Each restoration was finished immediately with fine diamond burrs and Sof-Lex disks (3 M, USA). The criteria that were evaluated by the USPHS method included: retention, color match, marginal integrity, marginal discoloration, and secondary caries. Results indicated that all compomer restorations were fully retained at 3 years, and that no secondary caries detected. Seven composite restorations were lost during the 3-year study. No statistical differences were observed between class III and class V or among other conditions (e.g., upper-lower arc, sex, age). This study demonstrates that compomers are suitable restorative materials for class III-V restorations. They may represent a clinical alternative to composites in class V and III restorations.

Adult↗
PubMed1998

In vitro and in vivo adhesion in operative dentistry: a review and evaluation.

Dentin and enamel bonding agents (DBAs) were introduced in the early 1980s to prevent volumetric shrinkage of composite resins used as restorative materials, to ensure dentin and enamel marginal sealing, and to prevent the dislocation of restorations during occlusal loading of the tooth. Today, DBAs play an important role in cosmetic and aesthetic dentistry and have radically altered the performance of operative dentistry. This article identifies the mechanical and physical properties of DBAs that facilitate the bonding of enamel, dentin, and various other restorations.

Adult↗
PubMed1997

Marginal morphology of Class V composite restorations.

PURPOSE: To evaluate the morphology of enamel and dentin margins of Class V restorations filled with different resin composites and glass ionomer cements by SEM examination of replicas. Microleakage was also evaluated between the restorative materials and dentin and enamel at different levels. MATERIALS AND METHODS: Non-retentive Class V cavities were prepared in extracted third molars on buccal and lingual surfaces at the CEJ level. Each material was used according to manufacturer's directions. Immediately after finishing, an impression of each restoration was made using a polyvinylsiloxane material to obtain an epoxy resin replica. Each replica was inspected under SEM to evaluate the morphology of the margin along the cervical-dentin and incisal-enamel junctions. Each tooth was then stored in dye solution (erythrosin B) for 24 hours. First an evaluation was made along the restoration margins to evaluate circumferential leakage. After longitudinal sectioning, leakage was calculated along the cavity wall in dentin and at the enamel interface (longitudinal leakage). RESULTS: Enamel margins were characterized (SEM) by prism fractures around restorations along with enamel chips and overhangs. These lesions were observed in about 30% of the samples. Dentin margins showed gaps along the dentin-bonding agents and fractures in the bonding agent/composite interface. Glass ionomers showed similar but fewer lesions both at enamel and dentin interfaces.

Adult↗
PubMed1997

Laboratory evaluation of compomers in Class V restorations.

PURPOSE: To evaluate the in vitro microleakage, marginal morphology and resin tags configuration of a compomer restorative material (Dyract) alternatively used with two different bonding systems (Dyract-PSA and Prime & Bond 2.0). A hybrid resin composite (Prisma TPH) used with two different bonding systems (Universal Bond 3 and ProBond) was evaluated as control material. MATERIALS AND METHODS: Class V non-retentive restorations were made in vitro at CEJ and divided at random in four groups: Dyract/PSA, Dyract/P&B 2.0, Prisma TPH/UB3, and Prisma TPH/ProBond. The latter two groups were as controls. After finishing the restorations, an impression material was used to obtain an epoxy resin replica for SEM analysis of margin alterations. Percentage of perfect margin was evaluated under SEM and calculated comparing it with the width/length of restoration margin. The presence of gaps, enamel fractures and other marginal alterations was also recorded inspecting under SEM replicas. Each tooth was then immersed for 24 hours in erythrosin B dye solution at room temperature and evaluated at superficial margins as marginal leakage (ML) for dye penetration. Each sample was then longitudinally sectioned, and leakage was expressed as % dye penetration of the total cavity wall, longitudinal leakage (LL). Finally, each tooth was dissolved (10%H3PO4 for 48 hours and NaOCl solution for additional 24 hours) to leave only the resin restoration. The internal walls of each restoration were then inspected by SEM at x1,000-15,000 to evaluate the presence of resin-dentin infiltrated layer (hybrid layer) and to calculate the ability of primer/bonding to infiltrate peritubular dentin and to form resin tags. RESULTS: Gap widths were 2-6 microns at dentin and lower at enamel. Several enamel fractures along the margin were observed. Resin tags were observed only in deeper dentin. Only Prime & Bond 2.0/Dyract formed resin tags at medium-superficial dentin. The length of resin tags ranged from 1-6 microns for Dyract-PSA primer to 100 microns for Prime & Bond 2.0. Marginal and longitudinal leakage was observed both at dentin and enamel levels. The best dentin seal was obtained with Prime & Bond 2.0/Dyract, while enamel seals were equivalent with both bonding systems (P > 0.05). No correlations were demonstrated between leakage and SEM observations.

Adult↗
PubMed1997

[Treatment of dentin sensitivity with stannous fluoride gel. Electron microscopic study and evaluation of dentin permeability].

Dentine hypersensitivity still represent a major clinical problem only partially solved. The presence of exposed opened dentinal tubules has been demonstrated increase the dentine permeability and it is the responsible for pain and sensitivity. Stannous fluoride solution has been recently proposed to reduce dentine hypersensitivity. The aim of the present study was to evaluate the dentinal permeability of a new stannous fluoride gel proposed for the therapy of dentine hypersensitivity. Human extracted teeth have been used and mounted and connected with a hydraulic pressure apparatus working at 1 psi (70 cm of water pressure). It was calculated the permeability of untreated smear layer, treated smear layer (after gel application) and after acidic treatment. It was observed that gel treatment was able to reduce dentine permeability. Scanning electron microscopy demonstrated the presence of a homogeneous smear layer after treatment with gel. This in vitro study confirms that stannous fluoride treatment has the capacity to modify dentine permeability of sensitive dentine.

Dentin↗
PubMed1995

Dentine permeability and bond quality as affected by new bonding systems.

OBJECTIVES AND METHODS: The relationship between dentine bonding and the condition of dentine for four dentine bonding systems (All Bond 2, Clearfil Liner Bond, Scotchbond MP and XR Bond) has been examined. Different dentine conditions were evaluated and correlated with adhesion values. Dentine permeability was calculated using a hydraulic pressure apparatus working under physiological pulpal pressure (6.9 kPa), while remaining dentine thickness (RDT) was measured using pincer calipers. Scanning electron microscopic (SEM) examinations were effected to analyse dentine morphology. These evaluations were considered as an index of the condition of dentine. Shear bond strength tests were used to evaluate adhesion. Dentine samples after the bonding systems application were stored for 24 h under pulpal pressure before bond strength was tested. RESULTS: Scanning electron microscopy examinations indicated that the application of bonding system conditioners caused the removal of smear layer, the demineralization of dentine and the formation of a layer of collapsed collagen fibrils in the intertubular and peritubular dentine. Primers were able to infiltrate the collagen fibrils. A layer of resin infiltrated/reinforced dentine (the so-called 'hybrid layer') was observed for All Bond 2, Clearfil Linear Bond and Schotchbond MP. CONCLUSIONS: Significant correlations were observed only for XR Bond, which proved very sensitive to RDT and dentine permeability despite the presence of smear layer. The other three materials did not show any correlation with dentine conditions. By contrast they showed the highest bond values.

Acid Etching, Dental↗
PubMed1995

[A morphological analysis and assessment of the dentinal permeability of detergents and liners].

In this study we evaluated the morphological aspect at scanning electron microscopy (SEM) and the degree of permeability of the dentinal surface after treatment with different detergent solutions, liners and cleansers. In particular we tested new potassium oxalate products. The results obtained with in vitro tests showed that many detergents, liners and cleansers are able to maintain almost unaltered the smear layer, causing small modifications for the diameter and the number of dentinal tubules which are partially exposed. The materials we used were able to deterge the dentinal surface, as demonstrated by SEM analysis, but one of them was able to stabilize and to protect the surface. All tested products, except potassium oxalate, caused an increase in dentinal permeability, proving to exercise a potential by damaging action towards the dentine and the pulpal tissue. Only DDS was able to reduce the dentinal permeability, causing the formation of calcium oxalate precipitates which occlude the dentinal tubules.

Dentin↗
PubMed1994

What is the clinical relevance of in vitro dentine permeability tests?

This paper reviews the effect of dentine permeability on the bond strength of dentinal bonding systems and its relationship with the morphology of dentine. Deep dentine is more permeable than superficial dentine. Demineralization of dentine surfaces with acidic conditioners significantly increases permeability with respect to dentine covered by a smear layer. Several primers apparently leave intact smear layers as seen by scanning electron microscopy, but greatly increase the fluid filtration towards the dentine suggesting several modifications in the smear layer. Previous generations of dentinal bonding systems have been shown to be extremely sensitive to dentine humidity and permeability. By contrast, contemporary dentine bonding systems are not influenced by wet dentine. According to the Poiseuille-Hagen equation, small changes in the functional diameter of dentinal tubules can greatly modify permeability. Restorative materials are able to reduce the permeability of prepared dentine subject to location.

Dental Bonding↗
PubMed1994

Permeability and microleakage of Class II resin composite restorations.

The aim of this study was to evaluate the variations in microleakage of large Class II (MOD) restorations over time. Three different combinations of dentine bonding agents and posterior resin composites which had previously shown promise were used: Vitrebond/Scotchbond 2 plus P50, Tripton plus Occlusin and Clearfil Photo Bond plus Clearfil Photo Posterior. Conventional Class II cavities were prepared in freshly extracted third molars. All gingival margins were terminated at the cemento-enamel junction. A fluid-under-pressure apparatus connected with the pulp chamber of each tooth was used to evaluate the permeability and marginal leakage of the restorations at 0.069 MPa. Microleakage was tested after insertion of restorations at 2, 15, 45, 150 min, after 1, 2, 7, 14 days, after 1, 2, 3 months, after thermal cycling and 10 months later, after occlusal loading. Finally, all specimens were exposed to silver nitrate solution to measure microleakage as dye penetration. Immediately after insertion of the restorations, all the materials showed a higher microleakage than after 1-2 days. After 4-8 weeks, all the restorations exhibited an increased permeability suggesting that hygroscopic expansion was not sufficient to keep pace with hydrolytic degradation of the restorations. Neither thermocycling or occlusal stresses increased the microleakage of the restorations.

Composite Resins↗
PubMed1994

Scanning electron microscopic evaluation of different endodontic procedures on dentin morphology of human teeth.

Four manual endodontic instruments, an ultrasonic and an endosonic system were studied with a view to evaluating the morphology of the smear layer and the amount of debris and pulpal residues in the apical third of human extracted straight teeth from 55- to 75-yr-old patients. The manual instruments were K files, Ergoflex files used with the step-back technique, Canal Master with its own technique, and Flex-R with the Roane technique. The ultrasonic system was Suprasson Piezo and the endosonic was Excalibur. Human extracted teeth with straight canals were used and examined under a scanning electron microscope. All manual instrumentations showed a homogeneous compact smear layer and no pulp residues. No statistical differences were observed among the four manual techniques. Ultrasonic technique showed the complete removal of the smear layer, leaving small amounts of pulp debris at the apical third, while the Excalibur showed an almost complete elimination of the smear layer, leaving a homogeneous layer of pulpal residues along the canal.

Aged↗
PubMed1993

Antibacterial effectiveness of dentin bonding systems.

This study examined the antibacterial activities of several commercially available glass ionomer cements, dentin bonding systems and luting agents by employing both agar plate diffusion (APD) and growth inhibition (GI) methods. Amalgam and resin composites were also tested as control materials. In both methods (APD and GI), cylindrical specimens were used. Four bacteria strains were tested: Streptococcus mutans, S. salivarius, S. mitis and S. sanguis. These studies were performed using standardized innoculums with selective media, and the assayed materials were directly applied on the assay cultures and plates. The results of agar plate assay were in accordance with the results of growth inhibition method. The glass ionomer cements showed marked antibacterial activity. On the contrary, amalgam, composites, luting agents and dentinal bonding systems did not affect bacterial growth. The sensitivity of the growth method showed that all the strains were inhibited in the same way by each inhibitory material. The data suggest that the use of glass ionomer cements as cavity liners/bases may reduce the consequences of microleakage due to its antibacterial properties.

Analysis of Variance↗